Posthypothermic rewarming considerations following traumatic brain injury

Vitreoretinal Surgery with Temperature Management: A Preliminary Study in Rabbits

The present study aimed to evaluate the structure of the rabbit retina after vitreoretinal surgery using prolonged irrigation with solutions of different temperatures. Thirty-six rabbits (72 eyes) were included in this study and randomly divided into 3 equal groups according to the temperature of the intraocular irrigating fluid they received during vitrectomy. Vitreoretinal surgery was performed with a 5°C irrigation solution in group 1 (12 rabbits, 24 eyes), a 22°C irrigation solution in group 2 (12 rabbits, 24 eyes), and a 36°C irrigation solution in group 3 (12 rabbits, 24 eyes). In each group of animals, the mean irrigation/aspiration time was 30 minutes for left eyes and 60 minutes for right eyes. Histological examination of the retina was performed 1, 7, and 30 days after surgery. During surgery, the temperature in the vitreous cavity of the eyes of rabbits of groups 1, 2, and 3 dropped by 26.0°C, 11.2°C (deep hypothermia), and 1.0°C (mild hypothermia), respectively. The highest rewarming rate was detected in group 1 (0.9°C/min) compared with group 2 (0.7°C/min) and group 3 (0.2°C/min). After 60 minutes of irrigation, retinal structural changes were detected in the animals of groups 1 and 2 (in contrast to the animals of group 3). After surgery with irrigation lasting 30 minutes, no retinal structural changes were observed. This study showed that temperature management, avoidance of intraoperative deep hypothermia, and prevention of rapid uncontrolled rewarming may protect the retinal morphology and increase the safety of prolonged vitreoretinal surgery.

Targeted Temperature Management in Cardiac Arrest: An Updated Narrative Review

The established benefits of cooling along with development of sophisticated methods to safely and precisely induce, maintain, monitor, and reverse hypothermia have led to the development of targeted temperature management (TTM). Early trials in human subjects showed that hypothermia conferred better neurological outcomes when compared to normothermia among survivors of cardiac arrest, leading to guidelines recommending targeted hypothermia in this patient population. Multiple studies have sought to explore and compare the benefit of hypothermia in various subgroups of patients, such as survivors of out-of-hospital cardiac arrest versus in-hospital cardiac arrest, and survivors of an initial shockable versus non-shockable rhythm. Larger and more recent trials have shown no statistically significant difference in neurological outcomes between patients with targeted hypothermia and targeted normothermia; further, aggressive cooling is associated with a higher incidence of multiple systemic complications. Based on this data, temporal trends have leaned towards using a lenient temperature target in more recent times. Current guidelines recommend selecting and maintaining a constant target temperature between 32 and 36 °C for those patients in whom TTM is used (strong recommendation, moderate-quality evidence), as soon as possible after return of spontaneous circulation is achieved and airway, breathing (including mechanical ventilation), and circulation are stabilized. The comparative benefit of lower (32-34 °C) versus higher (36 °C) temperatures remains unknown, and further research may help elucidate this. Any survivor of cardiac arrest who is comatose (defined as unarousable unresponsiveness to external stimuli) should be considered as a candidate for TTM regardless of the initial presenting rhythm, and the decision to opt for targeted hypothermia versus targeted normothermia should be made on a case-by-case basis.

Hypothermia for Acute Spinal Cord Injury

Neuroprotection after acute spinal cord injury is an important strategy to limit secondary injury. Animal studies have shown that systemic hypothermia is an effective neuroprotective strategy that can be combined with other therapies. Systemic hypothermia affects several processes at the cellular level to reduce metabolic activity, oxidative stress, and apoptotic neuronal cell death. Modest systemic hypothermia has been shown to be safe and feasible in the acute phase after cervical spinal cord injury. These data have provided the impetus for an active multicenter randomized controlled trial for modest systemic hypothermia in acute cervical spinal cord injury.

Anatomical Correlates and Surgical Considerations for Localized Therapeutic Hypothermia Application in Cochlear Implantation Surgery

Application of localized, mild therapeutic hypothermia during cochlear implantation (CI) surgery is feasible for residual hearing preservation.

Systemic Inflammatory Response Syndrome (SIRS) Score Independently Predicts Poor Outcome in Isolated Traumatic Brain Injury

INTRODUCTION

Systemic inflammatory response syndrome (SIRS) is frequently observed after various types of acute cerebral injury and has been linked to clinical deterioration in non-traumatic brain injury (TBI). SIRS scores have also been shown to be predictive of length of stay and mortality in trauma patients. We aimed to determine the prognostic utility of SIRS present at admission in trauma patients with isolated TBI.

METHODS

This was a 5-year retrospective cohort study of adults (≥18 years) with isolated TBI admitted to a Level II trauma center. The prognostic value of SIRS, total SIRS scores, and each SIRS criterion was examined by Χ ² and logistic regression analyses.

RESULTS

Of the 330 patients identified, 50 (15.2%) met SIRS criteria. SIRS was significantly associated with poor outcome (P < 0.001). Relative risk of poor outcome was 2.7 times higher in patients with a SIRS score of 2 on admission (P = 0.007) and increased significantly to 6.5 times in patients with a SIRS score of 3 (P = 0.002). Logistic regression demonstrated SIRS and each criterion to be significant independent prognostic factors (SIRS, P = 0.030; body temperature, P = 0.006; tachypnea, P = 0.022, tachycardia P = 0.023).

CONCLUSION

SIRS at admission is an independent predictor of poor outcome in isolated TBI patients. These data demonstrate SIRS to be an important clinical tool that may be used in facilitating prognostication, particularly in elderly trauma patients. Future prospective studies aimed at therapeutic interventions to mitigate SIRS in TBI patients are warranted.

LEVEL OF EVIDENCE

Prognostic, Level III.

Can we further optimize therapeutic hypothermia for hypoxic-ischemic encephalopathy?

Perinatal hypoxic-ischemic encephalopathy is a leading cause of neonatal death and disability. Therapeutic hypothermia significantly reduces death and major disability associated with hypoxic-ischemic encephalopathy; however, many infants still experience lifelong disabilities to movement, sensation and cognition. Clinical guidelines, based on strong clinical and preclinical evidence, recommend therapeutic hypothermia should be started within 6 hours of birth and continued for a period of 72 hours, with a target brain temperature of 33.5 ± 0.5°C for infants with moderate to severe hypoxic-ischemic encephalopathy. The clinical guidelines also recommend that infants be rewarmed at a rate of 0.5°C per hour, but this is not based on strong evidence. There are no randomized controlled trials investigating the optimal rate of rewarming after therapeutic hypothermia for infants with hypoxic-ischemic encephalopathy. Preclinical studies of rewarming are conflicting and results were confounded by treatment with sub-optimal durations of hypothermia. In this review, we evaluate the evidence for the optimal start time, duration and depth of hypothermia, and whether the rate of rewarming after treatment affects brain injury and neurological outcomes.

Slow rewarming improved the neurological outcomes of prolonged mild therapeutic hypothermia in patients with severe traumatic brain injury and an evacuated hematoma

Mild therapeutic hypothermia (MTH) is expected to improve the neurological outcomes of patients with severe traumatic brain injury (TBI). However, there are no standard protocols for managing the temperature of patients with severe TBI in order to improve their neurological outcomes. We conducted a post hoc analysis of the B-HYPO study, a randomized controlled trial of MTH in patients with TBI in Japan. We evaluated the impact of MTH methods on neurological outcomes. Ninety-seven patients who received MTH were included in the present analyses. The neurological outcomes were compared among subgroups of patients divided by cutoff values for the induction, maintenance, and rewarming times of MTH in all patients, in patients with diffuse injury, and in patients with an evacuated hematoma. The proportion of patients with a good neurological outcome was significantly different between patients with an evacuated hematoma divided into subgroups by the cutoff value of rewarming time of 48 h (>48 h vs. ≤ 48 h: 65% vs. 22%; odds ratio: 6.61; 95% confidence interval: 1.13-38.7, P = 0.0498). Slow rewarming for >48 h might improve the neurological outcomes of prolonged MTH in patients with TBI and an evacuated hematoma. Further studies are needed to investigate the optimal rewarming protocol in patients with TBI.

Therapeutic hypothermia and targeted temperature management for traumatic brain injury: Experimental and clinical experience

Traumatic brain injury (TBI) is a worldwide medical problem, and currently, there are few therapeutic interventions that can protect the brain and improve functional outcomes in patients. Over the last several decades, experimental studies have investigated the pathophysiology of TBI and tested various pharmacological treatment interventions targeting specific mechanisms of secondary damage. Although many preclinical treatment studies have been encouraging, there remains a lack of successful translation to the clinic and no therapeutic treatments have shown benefit in phase 3 multicenter trials. Therapeutic hypothermia and targeted temperature management protocols over the last several decades have demonstrated successful reduction of secondary injury mechanisms and, in some selective cases, improved outcomes in specific TBI patient populations. However, the benefits of therapeutic hypothermia have not been demonstrated in multicenter randomized trials to significantly improve neurological outcomes. Although the exact reasons underlying the inability to translate therapeutic hypothermia into a larger clinical population are unknown, this failure may reflect the suboptimal use of this potentially powerful therapeutic in potentially treatable severe trauma patients. It is known that multiple factors including patient recruitment, clinical treatment variables, and cooling methodologies are all important in yielding beneficial effects. High-quality multicenter randomized controlled trials that incorporate these factors are required to maximize the benefits of this experimental therapy. This article therefore summarizes several factors that are important in enhancing the beneficial effects of therapeutic hypothermia in TBI. The current failures of hypothermic TBI clinical trials in terms of clinical protocol design, patient section, and other considerations are discussed and future directions are emphasized.

Targeted temperature management in the ICU: Guidelines from a French expert panel

Over the recent period, the use of induced hypothermia has gained an increasing interest for critically ill patients, in particular in brain-injured patients. The term "targeted temperature management" (TTM) has now emerged as the most appropriate when referring to interventions used to reach and maintain a specific level temperature for each individual. TTM may be used to prevent fever, to maintain normothermia, or to lower core temperature. This treatment is widely used in intensive care units, mostly as a primary neuroprotective method. Indications are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of TTM in adult and paediatric critically ill patients developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de réanimation de langue française [SRLF]) and the French Society of Anesthesia and Intensive Care Medicine (Société francaise d'anesthésie réanimation [SFAR]) with the participation of the French Emergency Medicine Association (Société française de médecine d'urgence [SFMU]), the French Group for Pediatric Intensive Care and Emergencies (Groupe francophone de réanimation et urgences pédiatriques [GFRUP]), the French National Association of Neuro-Anesthesiology and Critical Care (Association nationale de neuro-anesthésie réanimation française [ANARLF]), and the French Neurovascular Society (Société française neurovasculaire [SFNV]). Fifteen experts and two coordinators agreed to consider questions concerning TTM and its practical implementation in five clinical situations: cardiac arrest, traumatic brain injury, stroke, other brain injuries, and shock. This resulted in 30 recommendations: 3 recommendations were strong (Grade 1), 13 were weak (Grade 2), and 14 were experts' opinions. After two rounds of rating and various amendments, a strong agreement from voting participants was obtained for all 30 (100%) recommendations, which are exposed in the present article.

Targeted temperature management in the ICU: guidelines from a French expert panel

Over the recent period, the use of induced hypothermia has gained an increasing interest for critically ill patients, in particular in brain-injured patients. The term “targeted temperature management” (TTM) has now emerged as the most appropriate when referring to interventions used to reach and maintain a specific level temperature for each individual. TTM may be used to prevent fever, to maintain normothermia, or to lower core temperature. This treatment is widely used in intensive care units, mostly as a primary neuroprotective method. Indications are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of TTM in adult and paediatric critically ill patients developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de Réanimation de Langue Française [SRLF]) and the French Society of Anesthesia and Intensive Care Medicine (Société Francaise d’Anesthésie Réanimation [SFAR]) with the participation of the French Emergency Medicine Association (Société Française de Médecine d’Urgence [SFMU]), the French Group for Pediatric Intensive Care and Emergencies (Groupe Francophone de Réanimation et Urgences Pédiatriques [GFRUP]), the French National Association of Neuro-Anesthesiology and Critical Care (Association Nationale de Neuro-Anesthésie Réanimation Française [ANARLF]), and the French Neurovascular Society (Société Française Neurovasculaire [SFNV]). Fifteen experts and two coordinators agreed to consider questions concerning TTM and its practical implementation in five clinical situations: cardiac arrest, traumatic brain injury, stroke, other brain injuries, and shock. This resulted in 30 recommendations: 3 recommendations were strong (Grade 1), 13 were weak (Grade 2), and 14 were experts’ opinions. After two rounds of rating and various amendments, a strong agreement from voting participants was obtained for all 30 (100%) recommendations, which are exposed in the present article.

Epidural focal brain cooling abolishes neocortical seizures in cats and non-human primates

Focal brain cooling (FBC) is under investigation in preclinical trials of intractable epilepsy (IE), including status epilepticus (SE). This method has been studied in rodents as a possible treatment for epileptic disorders, but more evidence from large animal studies is required. To provide evidence that FBC is a safe and effective therapy for IE, we investigated if FBC using a titanium cooling plate can reduce or terminate focal neocortical seizures without having a significant impact on brain tissue. Two cats and two macaque monkeys were chronically implanted with an epidural FBC device over the somatosensory and motor cortex. Penicillin G was delivered via the intracranial cannula for induction of local seizures. Repetitive FBC was performed using a cooling device implanted for a medium-term period (FBC for 30min at least twice every week; 3 months total) in three of the four animals. The animals exhibited seizures with repetitive epileptiform discharges (EDs) after administration of penicillin G, and these discharges decreased at less than 20°C cooling with no adverse histological effects. The results of this study suggest that epidural FBC is a safe and effective potential treatment for IE and SE.

Efficacy of Selective Brain Cooling Using a Nasopharyngeal Method in Piglets

BACKGROUND

Mild hypothermia is an effective neuroprotective strategy for a variety of acute brain injuries. Cooling the nasopharynx may offer the capability to cool the brain selectively due to anatomic proximity of the internal carotid artery to the cavernous sinus. This study investigated the feasibility and efficiency of nasopharyngeal brain cooling by continuously blowing room temperature or cold air at different flow rates into the nostrils of normal newborn piglets.

METHODS

Experiments were conducted on thirty piglets (n = 30, weight = 2.7 ± 1.5 kg). Piglets were anesthetized with 1–2% isoflurane and were randomized to receive one of four different nasopharyngeal cooling treatments: I. Room temperature at a flow rate of 3–4 L min(−1) (n = 6); II. −1 ± 2 °C at a flow rate of 3–4 L min(−1) (n = 6); III. Room temperature at a flow rate of 14–15 L min(−1) (n = 6); IV. −8 ± 2 °C at a flow rate of 14–15 L min(−1) (n = 6). To control for the normal thermal regulatory response of piglets without nasopharyngeal cooling, a control group of piglets (n = 6) had their brain temperature monitored without nasopharyngeal cooling. The duration of treatment was 60 min, with additional 30 min of observation.

RESULTS

In group I, median cooling rate was 1.7 ± 0.9 °C/h by setting the flow rate of room temperature air to 3–4 L min(−1). Results of comparing different temperatures and flow rates in the nasopharyngeal cooling approach reveal that the brain temperature could be reduced rapidly at a rate of 5.5 ± 1.1 °C/h by blowing −8 ± 2 °C air at a flow rate of 14–15 L min(−1).

CONCLUSIONS

Nasopharyngeal cooling via cooled insufflated air can lower the brain temperature, with higher flows and lower temperatures of insufflated air being more effective.

A new approach to selective brain cooling by a Ranque-Hilsch vortex tube

Background

Target temperature management is the single most effective intervention and the gold standard in post-resuscitation care today. However, cooling the whole body below 33–34 °C can cause severe complications. Therefore, developing a selective brain cooling (SBC) approach which can be initiated early to induce rapid cooling and maintain the target temperature over 12–24 h before slowly rewarming brain temperature by itself alone would be advantageous. Vortex tubes are simple mechanical devices generating cold air from a stream of compressed air without applied chemical or energy. This study investigated whether blowing cooled air from a vortex tube into the nasal cavities is safe and effective to selectively reduce and maintain before slowly rewarming brain temperature back to normal temperature.

Methods

Experiments were conducted on ten juvenile pigs. Body temperature was measured using an esophageal and a rectal temperature probe while brain temperature with an intraparenchymal thermocouple probe. Cerebral blood flow (CBF) was measured with CT perfusion.

Results

Brain temperature dropped below 34 °C within 30–40 min while a brain-esophageal temperature difference greater than 3 °C was maintained over 6 h. There was no evidence of nasal or nasopharynx mucosal swelling, necrosis, or hemorrhage on MRI examination. CBF first decreased and then stabilized together with brain temperature before increasing to the baseline level during rewarming.

Conclusions

SBC was accomplished by blowing cold air from a vortex tube into the nasal cavities. Due to its portability, the method can be used continuously in resuscitated patients in both in- and out-of-hospital situations without interruption.

Morbidity and mortality associated with rewarming hypothermic very low birth weight infants

OBJECTIVES

In very low birthweight (VLBW) infants, hypothermia is associated with poor outcomes. The goal of this study is to assess the relationship between the rate of rewarming these babies and their outcomes.

METHODS

This is a retrospective cohort study of 98 inborn VLBW infants who were hypothermic (<36°C rectally) upon admission to the NICU. A logistic regression model was used to examine the relationship between the rates of rewarming and time to achieve euthermia and the following outcomes: death, intraventricular hemorrhage, severe intraventricular hemorrhage, bronchopulmonary dysplasia, necrotizing enterocolitis and retinopathy of prematurity.

RESULTS

Prolonged rewarming time was associate with increased odds of mortality (OR 1.273 95% CI 1.032-1.571). No associations between rewarming rates and any of the outcomes were seen. Once birthweight was included in a multiple logistic regression model, the association between mortality and rewarming time was no longer significant. Outcomes that were not associated with either rate or time of rewarming (even in a univariate model) were: bronchopulmonary dysplasia, intraventricular hemorrhage, severe intraventricular hemorrhage, necrotizing enterocolitis and retinopathy of prematurity.

CONCLUSION

In moderately hypothermic VLBW infants, after accounting for birthweight, no association between rewarming and outcome is seen.

Hypothermia in Traumatic Brain Injury

For over 50 years, clinicians have used hypothermia to manage traumatic brain injury (TBI). In the last two decades numerous trials have assessed whether hypothermia is of benefit in patients. Mild to moderate hypothermia reduces the intracranial pressure (ICP). Randomized control trials for short-term hypothermia indicate no benefit in outcome after severe TBI, whereas longer-term hypothermia could be of benefit by reducing ICP. This article summarises current evidence and gives recommendations based upon the conclusions.

Targeted temperature management in traumatic brain injury

Traumatic brain injury (TBI) is recognized as the significant cause of mortality and morbidity in the world. To reduce unfavorable outcome in TBI patients, many researches have made much efforts for the innovation of TBI treatment. With the results from several basic and clinical studies, targeted temperature management (TTM) including therapeutic hypothermia (TH) have been recognized as the candidate of neuroprotective treatment. However, their evidences are not yet proven in larger randomized controlled trials (RCTs). The main aim of this review is thus to clarify specific pathophysiology which TTM will be effective in TBI. Historically, there were several clinical trials which compare TH and normothermia. Recently, two RCTs were able to demonstrate the significant beneficial effects of TTM in one specific pathology, patients with mass evacuated lesions. These suggested that TTM might be effective especially for the ischemic-reperfusional pathophysiology of TBI, like as acute subdural hematoma which needs to be evacuated. Also, the latest preliminary report of European multicenter trial suggested the promising efficacy of reduction of intracranial pressure in TBI. Conclusively, TTM is still in the center of neuroprotective treatments in TBI. This therapy is expected to mitigate ischemic and reperfusional pathophysiology and to reduce intracranial pressure in TBI. Further results from ongoing clinical RCTs are waited.

Rapid and selective brain cooling method using vortex tube: A feasibility study

Vortex tubes are simple mechanical devices to produce cold air from a stream of compressed air without any moving parts. The primary focus of the current study is to investigate the feasibility and efficiency of nasopharyngeal brain cooling method using a vortex tube. Experiments were conducted on 5 juvenile pigs. Nasopharygeal brain cooling was achieved by directing cooled air via a catheter in each nostril into the nasal cavities. A vortex tube was used to generate cold air using various sources of compressed air: (I) hospital medical air outlet (n = 1); (II) medical air cylinders (n = 3); and (III) scuba (diving) cylinders (n = 1). By using compressed air from a hospital medical air outlet at fixed inlet pressure of 50 PSI, maximum brain-rectal temperature gradient of -2°C was reached about 45-60 minutes by setting the flow rate of 25 L/min and temperature of -7°C at the cold air outlet. Similarly, by using medical air cylinders at fill-pressure of 2265 PSI and down regulate the inlet pressure to the vortex tube to 50 PSI, brain temperature could be reduced more rapidly by blowing -22°C ± 2°C air at a flow rate of 50 L/min; brain-body temperature gradient of -8°C was obtained about 30 minutes. Furthermore, we examined scuba cylinders as a portable source of compressed gas supply to the vortex tube. Likewise, by setting up the vortex tube to have an inlet pressure of 25 PSI and 50 L/min and -3°C at the cold air outlet, brain temperature decreased 4.5°C within 10-20 min.

Therapeutic hypothermia and targeted temperature management in traumatic brain injury: Clinical challenges for successful translation

The use of therapeutic hypothermia (TH) and targeted temperature management (TTM) for severe traumatic brain injury (TBI) has been tested in a variety of preclinical and clinical situations. Early preclinical studies showed that mild reductions in brain temperature after moderate to severe TBI improved histopathological outcomes and reduced neurological deficits. Investigative studies have also reported that reductions in post-traumatic temperature attenuated multiple secondary injury mechanisms including excitotoxicity, free radical generation, apoptotic cell death, and inflammation. In addition, while elevations in post-traumatic temperature heightened secondary injury mechanisms, the successful implementation of TTM strategies in injured patients to reduce fever burden appear to be beneficial. While TH has been successfully tested in a number of single institutional clinical TBI studies, larger randomized multicenter trials have failed to demonstrate the benefits of therapeutic hypothermia. The use of TH and TTM for treating TBI continues to evolve and a number of factors including patient selection and the timing of the TH appear to be critical in successful trial design. Based on available data, it is apparent that TH and TTM strategies for treating severely injured patients is an important therapeutic consideration that requires more basic and clinical research. Current research involves the evaluation of alternative cooling strategies including pharmacologically-induced hypothermia and the combination of TH or TTM approaches with more selective neuroprotective or reparative treatments. This manuscript summarizes the preclinical and clinical literature emphasizing the importance of brain temperature in modifying secondary injury mechanisms and in improving traumatic outcomes in severely injured patients. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Cold stress protein RBM3 responds to temperature change in an ultra-sensitive manner in young neurons

Extremely mild hypothermia to 36.0 °C is not thought to appreciably differ clinically from 37.0 °C. However, it is possible that 36.0 °C stimulates highly sensitive hypothermic signaling mechanism(s) and alters biochemistry. To the best of our knowledge, no such ultra-sensitive pathway/mechanisms have been described. Here we show that cold stress protein RNA binding motif 3 (RBM3) increases in neuron and astrocyte cultures maintained at 33 °C or 36 °C for 24 or 48 h, compared to 37 °C controls. Neurons cultured at 36 °C also had increased global protein synthesis (GPS). Finally, we found that melatonin or fibroblast growth factor 21 (FGF21) augmented RBM3 upregulation in young neurons cooled to 36 °C. Our results show that a 1 °C reduction in temperature can induce pleiotropic biochemical changes by upregulating GPS in neurons which may be mediated by RBM3 and that this process can be pharmacologically mimicked and enhanced with melatonin or FGF21.

A Systematic Review of the Effects of Body Temperature on Outcome After Adult Traumatic Brain Injury

OBJECTIVE

This systematic review describes effects of body temperature alterations defined as fever, controlled normothermia, and spontaneous or induced hypothermia on outcome after traumatic brain injury (TBI) in adults.

DATA SOURCES

A search was conducted using PubMed, Cochrane Library database, Cumulative Index to Nursing and Allied Health Literature, EMBASE, and ISI Web of Science in July 2013 with no back date restriction except for induced hypothermia (2009).

STUDY SELECTION

Of 1366 titles identified, 712 were reviewed. Sixteen articles met inclusion criteria: randomized controlled trials in hypothermia since 2009 (last Cochrane review) or cohort studies of temperature in TBI, measure core and/or brain temperature, neurologic outcome reporting, primarily adult patients, and English language publications. Exclusion criteria were as follows: most patients with non-TBI diagnosis, primarily pediatric patients, case reports, or laboratory/animal studies.

DATA SYNTHESIS

Most studies found that fever avoidance resulted in positive outcomes including decreased length of stay in the intensive care unit; mortality; and incidence of hypertension, elevated intracranial pressure, and tachycardia. Hypothermia on admission correlated with poor outcomes. Controlled normothermia improved surrogate outcomes. Prophylactic induced hypothermia is not supported by the available evidence from randomized controlled trial.

CONCLUSION

Setting a goal of normothermia, avoiding fever, and aggressively treating fever may be most important after TBI. Further research is needed to characterize the magnitude and duration of temperature alteration after TBI, determine if temperature alteration influences or predicts neurologic outcome, determine if rate of temperature change influences or predicts neurologic outcome, and compare controlled normothermia versus standard practice or hypothermia.

Therapeutic Hypothermia in Spinal Cord Injury: The Status of Its Use and Open Questions

Spinal cord injury (SCI) is a major health problem and is associated with a diversity of neurological symptoms. Pathophysiologically, dysfunction after SCI results from the culmination of tissue damage produced both by the primary insult and a range of secondary injury mechanisms. The application of hypothermia has been demonstrated to be neuroprotective after SCI in both experimental and human studies. The myriad of protective mechanisms of hypothermia include the slowing down of metabolism, decreasing free radical generation, inhibiting excitotoxicity and apoptosis, ameliorating inflammation, preserving the blood spinal cord barrier, inhibiting astrogliosis, promoting angiogenesis, as well as decreasing axonal damage and encouraging neurogenesis. Hypothermia has also been combined with other interventions, such as antioxidants, anesthetics, alkalinization and cell transplantation for additional benefit. Although a large body of work has reported on the effectiveness of hypothermia as a neuroprotective approach after SCI and its application has been translated to the clinic, a number of questions still remain regarding its use, including the identification of hypothermia's therapeutic window, optimal duration and the most appropriate rewarming rate. In addition, it is necessary to investigate the neuroprotective effect of combining therapeutic hypothermia with other treatment strategies for putative synergies, particularly those involving neurorepair.

Lawrence K, Lee TY. Coupling of cerebral blood flow and oxygen consumption during hypothermia in newborn piglets as measured by time-resolved near-infrared spectroscopy: a pilot study

Hypothermia (HT) is a potent neuroprotective therapy that is now widely used in following neurological emergencies, such as neonatal asphyxia. An important mechanism of HT-induced neuroprotection is attributed to the associated reduction in the cerebral metabolic rate of oxygen ([Formula: see text]). Since cerebral circulation and metabolism are tightly regulated, reduction in [Formula: see text] typically results in decreased cerebral blood flow (CBF); it is only under oxidative stress, e.g., hypoxia-ischemia, that oxygen extraction fraction (OEF) deviates from its basal value, which can lead to cerebral dysfunction. As such, it is critical to measure these key physiological parameters during therapeutic HT. This report investigates a noninvasive method of measuring the coupling of [Formula: see text] and CBF under HT and different anesthetic combinations of propofol/nitrous-oxide ([Formula: see text]) that may be used in clinical practice. Both CBF and [Formula: see text] decreased with decreasing temperature, but the OEF remained unchanged, which indicates a tight coupling of flow and metabolism under different anesthetics and over the mild HT temperature range (38°C to 33°C).

Interpreting the results of the targeted temperature management trial in cardiac arrest

The targeted temperature management (TTM) trial, which found that cooling to 33°C after witnessed cardiac arrest (CA) conferred no benefits compared with 36°C, has led to much debate in the hypothermia community. This article discusses what lessons can be drawn. The TTM trial achieved far better outcomes in controls than any previous randomized controlled trial (RCT) or any nonrandomized study where no fever control was applied. On the other hand, rates of good outcomes in the hypothermia group were somewhat lower than in previous RCTs and most nonrandomized studies. The TTM authors conclude that benefits of temperature management are derived exclusively from fever control and that further lowering of temperature confers no benefit. Indeed, without doubt, the TTM trial demonstrates the crucial importance of strict fever control after CA and that this provides sufficient neuroprotection for some patients. However, we argue that the hypothermia intervention was executed suboptimally (possibly inadvertent selection bias; late start of cooling, up to 4 hours after ROSC; slow cooling rates, 10 hours to target temperature; more rapid rewarming than previous studies; and some other issues). This could explain high rates of good outcomes in controls and lower-than-expected rates in patients cooled to 33°C compared with previous randomized and nonrandomized studies. Outside of two previous RCTs, the use of hypothermia after CA is supported by hundreds of animal experiments, evidence from 46 before-after studies and large registries, and indirect supporting evidence from 7 RCTs in newborns with neonatal asphyxia. In addition, one RCT found improved outcomes with 32°C compared with 34°C. It remains to be explained why the TTM results so completely contradict previous studies in this field. These issues should be thoroughly discussed before changes in guidelines and protocols are made. Ending or modifying hypothermia treatment after CA should require the strongest possible evidence.

Cooling techniques for targeted temperature management post-cardiac arrest

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2015 and co-published as a series in Critical Care. Other articles in the series can be found online at http://ccforum.com/series/annualupdate2015. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Targeted temperature management in brain protection: An evidence-based review

Targeted temperature management (TTM) for neuroprotection involves maintaining the temperature of the brain at predetermined levels by various techniques. It is aimed at avoiding the harmful effects of hyperthermia on the brain and at exploiting the protective effects of lower tissue temperature. There has been an explosion in the use of TTM for neuroprotection in a variety of clinical scenarios apart from the commonly accepted fields of resuscitation and ischaemic, hypoxic encephalopathy. This review briefly discusses the evidence base for TTM. The focus is on various areas of application for neuroprotection, the practical issues pertaining to TTM implementation, the recent data that support it and the present areas of controversy.

Recent advances and future directions of hypothermia therapy for traumatic brain injury

For severe traumatic brain injury (TBI) patients, no effective treatment method replacing hypothermia therapy has emerged, and hypothermia therapy still plays the major role. To increase its efficacy, first, early introduction is important. Since there are diverse pathologies of severe TBI, it is necessary to appropriately control the temperature in the hypothermia maintenance and rewarming phases by monitoring relative to the pathology. Currently, hypothermia is considered appropriate for severe TBI patients requiring craniotomy for removal of hematoma, while induced normothermia is appropriate for severe TBI patients with diffuse brain injury. Induced normothermia is expected to exhibit a cerebroprotective effect equivalent to hypothermia, as well as reduce the complexity of whole-body management and systemic complications. According to the Japan Neurotrauma Data Bank of the Japan Society of Neurotraumatology, the brain temperature was controlled in 43.9% of severe TBI patients (induced normothermia: 32.2%, hypothermia: 11.7%) in Japan. Brain temperature management was performed mainly in young patients, and the outcome on discharge was favorable in patients who received brain temperature management. Particularly, patients who need craniotomy for removal of hematoma were a good indication of therapeutic hypothermia. Improvement of therapeutic outcomes with widespread temperature management in TBI patients is expected.

Changes in glutamate concentration, glucose metabolism, and cerebral blood flow during focal brain cooling of the epileptogenic cortex in humans

OBJECTIVE

Recently, focal brain cooling (FBC) was proposed as a method for treating refractory epilepsy. However, the precise influence of cooling on the molecular basis of epilepsy has not been elucidated. Thus the aim of this study was to assess the effect of FBC on glutamate (Glu) concentration, cerebral blood flow (CBF), and glucose metabolism in patients with intractable epilepsy.

METHODS

Nine patients underwent FBC at 15°C for 30 min prior to cortical resection (n = 6) or hippocampectomy (n = 3). Measurement of metabolites and CBF, as well as electrocorticography (ECoG), was performed.

RESULTS

Epileptic discharge (ED), as observed by ECoG, disappeared in the cooling period and reappeared in the rewarming period. Glu concentrations were high during the precooling period and were reduced to 51.2% during the cooling period (p = 0.025). Glycerol levels showed a similar decrease (p = 0.028). Lactate concentration was high during the precooling period and was reduced during the cooling period (21.3% decrease; p = 0.005). Glucose and pyruvate levels were maintained throughout the procedure. Changes in CBF were parallel to those observed by ECoG.

SIGNIFICANCE

FBC reduced EDs and concentrations of Glu and glycerol. This demonstrates the neuroprotective effect of FBC. Our findings confirm that FBC is a reasonable and optimal treatment option for patients with intractable epilepsy.

Hypothermia and pharmacological regimens that prevent overexpression and overactivity of the extracellular calcium-sensing receptor protect neurons against traumatic brain injury

Traumatic brain injury (TBI) leads to acute functional deficit in the brain. Molecular events underlying TBI remain unclear. In mouse brains, we found controlled cortical impact (CCI) injury induced overexpression of the extracellular calcium-sensing receptor (CaSR), which is known to stimulate neuronal activity and accumulation of intracellular Ca(2+) and concurrent down-regulation of type B or metabotropic GABA receptor 1 (GABA-B-R1), a prominent inhibitory pathway in the brain. These changes in protein expression preceded and were closely associated with the loss of brain tissue, as indicated by the increased size of cortical cavity at impact sites, and the development of motor deficit, as indicated by the increased frequency of right-biased swing and turn in the CCI mice. Mild hypothermia, an established practice of neuroprotection for brain ischemia, partially but significantly blunted all of the above effects of CCI. Administration of CaSR antagonist NPS89636 mimicked hypothermia to reduce loss of brain tissue and motor functions in the CCI mice. These data together support the concept that CaSR overexpression and overactivity play a causal role in potentiating TBI potentially by stimulating excitatory neuronal responses and by interfering with inhibitory GABA-B-R signaling and that the CaSR could be a novel target for neuroprotection against TBI.

Therapeutic Hypothermia in Children and Adults with Severe Traumatic Brain Injury

Great expectations have been raised about neuroprotection of therapeutic hypothermia in patients with traumatic brain injury (TBI) by analogy with its effects after heart arrest, neonatal asphyxia, and drowning in cold water. The aim of this study is to review our present knowledge of the effect of therapeutic hypothermia on outcome in children and adults with severe TBI. A literature search for relevant articles in English published from year 2000 up to December 2013 found 19 studies. No signs of improvement in outcome from hypothermia were seen in the five pediatric studies. Varied results were reported in 14 studies on adult patients, 2 of which reported a tendency of higher mortality and worse neurological outcome, 4 reported lower mortality, and 9 reported favorable neurological outcome with hypothermia. The quality of several trials was low. The best-performed randomized studies showed no improvement in outcome by hypothermia-some even indicated worse outcome. TBI patients may suffer from hypothermia-induced pulmonary and coagulation side effects, from side effects of vasopressors when re-establishing the hypothermia-induced lowered blood pressure, and from a rebound increase in intracranial pressure (ICP) during and after rewarming. The difference between body temperature and temperature set by the biological thermostat may cause stress-induced worsening of the circulation and oxygenation in injured areas of the brain. These mechanisms may counteract neuroprotective effects of therapeutic hypothermia. We conclude that we still lack scientific support as a first-tier therapy for the use of therapeutic hypothermia in TBI patients for both adults and children, but it may still be an option as a second-tier therapy for refractory intracranial hypertension.

The effect of admission spontaneous hypothermia on patients with severe traumatic brain injury

INTRODUCTION

Recent information has emerged regarding the harmful effects of spontaneous hypothermia at time of admission in trauma patients. However the volume of evidence regarding the role of spontaneous hypothermia in TBI patients is inadequate.

METHODS

We performed secondary data analysis of 10 years of the Pennsylvania trauma outcome study (PTOS) database. Unadjusted comparisons of the association of admission spontaneous hypothermia with mortality were performed. In addition, full assessment of the association of hypothermia with mortality was conducted using multivariable logistic regressions reporting the odds ratios (OR) with the 95% confidence intervals (CI) and P-values.

RESULTS

There were 11,033 patients identified from the PTOS with severe TBI. There were 4839 deaths (43.9%). The proportion of deaths in hypothermic patients was higher than the proportion of deaths in normothermic patients (53.9% vs. 37.4% respectively; P value<0.001). In a multivariable logistic regression model adjusted for demographics, injury characteristics, and information at admission to the trauma centre, the odds of death among patients with hypothermia were 1.70 times the odds of death among patients with normothermia (OR 1.70, 95% CI 1.50-1.93), indicating that the probability of death was significantly higher when patients arrived hypothermic at the trauma centre.

CONCLUSION

The presence of spontaneous hypothermia at hospital admission is associated with a significant increase in the risk of mortality in patients with severe TBI. The benefit of maintaining normothermia in severe TBI patients, the impact of prolonged re-warming in patients with established hypothermia and the introduction of prophylactic measures to complications of hypothermia are key points that require further investigation.

Emerging therapies in neurorehabilitation

Just as advancing technology has furthered our understanding of how the nervous system recovers, technology also enables the development of novel approaches to treatment. Because nervous system disease and injury often lead to severely impaired function, patients and families are willing to try anything, so therapies are often adopted with little evidence that they actually work. Evidence shows that comprehensive rehabilitation programs produce better outcomes, but it is still not understood what components of these multifaceted programs are critical to their success. Functional neuroimaging and other modalities now allow monitoring of neurophysiologic changes that can be paired with assessments detailing clinical changes, furthering our understanding of the factors that influence the recovery process. This article discusses several novel and emerging therapies in neurorehabilitation as well as recent multistudy reviews of selected treatments.

Selective brain cooling in rats ameliorates intracerebral hemorrhage and edema caused by penetrating brain injury: possible involvement of heme oxygenase-1 expression

Brain edema formation associated with trauma-induced intracerebral hemorrhage (ICH) is a clinical complication with high mortality. Studies have shown that heme oxygenase-1 (HO-1) plays an important role in ICH-induced brain edema. In order to understand the role of HO-1 in the protective effect of selective brain cooling (SBC), we investigated the time course of HO-1 changes following penetrating ballistic-like brain injury (PBBI) in rats. Samples were collected from injured and control animals at 6, 24, 48, and 72 h, and 7 days post-injury to evaluate HO-1 expression, heme concentration, brain water content, and immunohistochemistry (IHC). Following a 10% frontal PBBI, HO-1 mRNA and protein was increased at all time points studied, reaching maximum expression levels at 24-48 h post-injury. An increase in the heme concentration and the development of brain edema coincided with the upregulation of HO-1 mRNA and protein during the 7-day post-injury period. SBC significantly decreased PBBI-induced heme concentration, attenuated HO-1 upregulation, and concomitantly reduced brain water content. These results suggest that the neuroprotective effects of SBC may be partially mediated by reducing the heme accumulation, which reduced injury-mediated upregulation of HO-1, and in turn ameliorated edema formation. Collectively, these results suggest a potential value of HO-1 as a diagnostic and/or therapeutic biomarker in hemorrhagic brain injury.

Prolonged hypothermia in rat: a safety study using brain-selective and systemic treatments

Hypothermia is an effective neuroprotectant for cardiac arrest and perinatal ischemic injury. Hypothermia also improves outcome after traumatic brain injury and stroke. Although the ideal treatment parameters (duration, delay, and depth) are not fully delineated, prolonged cooling is usually more effective than shorter periods. There is the concern that extended cooling may be hazardous to brain plasticity and cause damage. In order to evaluate this possibility, we assessed the effects of 3 days of systemic hypothermia (32°C) in rats subjected to a sham stroke surgery. There were no detrimental behavioral effects or signs of brain damage. As even longer cooling may be needed in some patients, we cooled (∼32°C) the right hemisphere of rats for 3 or 21 days. Physiological variables, functional outcome, and measures of cell injury were examined. Focal brain cooling for 21 days modestly decreased heart rate, blood pressure, and core temperature. However, focal hypothermia did not affect subsequent behavior (e.g., spontaneous limb usage), cell morphology (e.g., dendritic arborization, ultrastructure), or cause cell death. In conclusion, prolonged mild hypothermia did not harm the brain of normal animals. Further research is now needed to evaluate whether such treatments affect plasticity after brain injury.

Therapeutic hypothermia for the management of intracranial hypertension in severe traumatic brain injury: a systematic review

BACKGROUND

Traumatic brain injury (TBI) is a major source of death and severe disability worldwide. Raised Intracranial pressure (ICP) is an important predictor of mortality in patients with severe TBI and aggressive treatment of elevated ICP has been shown to reduce mortality and improve outcome. The acute post-injury period in TBI is characterized by several pathophysiologic processes that start in the minutes to hours following injury. All of these processes are temperature-dependent; they are all aggravated by fever and inhibited by hypothermia.

METHODS

This study reviewed the current clinical evidence in support of the use of therapeutic hypothermia (TH) for the treatment of intracranial hypertension (ICH) in patients with severe TBI.

RESULTS

This study identified a total of 18 studies involving hypothermia for control of ICP; 13 were randomized controlled trials (RCT) and five were observational studies. TH (32-34°C) was effective in controlling ICH in all studies. In the 13 RCT, ICP in the TH group was always significantly lower than ICP in the normothermia group. In the five observational studies, ICP during TH was always significantly lower than prior to inducing TH.

CONCLUSIONS

Pending results from large multi-centre studies evaluating the effect of TH on ICH and outcome, TH should be included as a therapeutic option to control ICP in patients with severe TBI.

Facts and fiction: the impact of hypothermia on molecular mechanisms following major challenge

Numerous multiple trauma and surgical patients suffer from accidental hypothermia. While induced hypothermia is commonly used in elective cardiac surgery due to its protective effects, accidental hypothermia is associated with increased posttraumatic complications and even mortality in severely injured patients. This paper focuses on protective molecular mechanisms of hypothermia on apoptosis and the posttraumatic immune response. Although information regarding severe trauma is limited, there is evidence that induced hypothermia may have beneficial effects on the posttraumatic immune response as well as apoptosis in animal studies and certain clinical situations. However, more profound knowledge of mechanisms is necessary before randomized clinical trials in trauma patients can be initiated.

The Use of Hypothermia Therapy in Traumatic Ischemic / Reperfusional Brain Injury: Review of the Literatures

Therapeutic mild hypothermia has been used widely in brain injury. It has evaluated in numerous clinical trials, and there is strong evidence for the use of hypothermia in treating patients with several types of ischemic / reperfusional (I/R) injuries, examples being cardiac arrest and neonatal hypoxic-ischemic encephalopathy.In spite of many basic research projects demonstrating effectiveness, therapeutic hypothermia has not been proven effective for the heterogeneous group of traumatic brain injury patients in multicenter clinical trials. In the latest clinical trial, however, researchers were able to demonstrate the significant beneficial effects of hypothermia in one specific group; patients with mass evacuated lesions. This suggested that mild therapeutic hypothermia might be effective for I/R related traumatic brain injury.In this article we have reviewed much of the previous literature concerning the mechanisms of I/R injury to the protective effects of mild therapeutic hypothermia.